/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.zookeeper.server.persistence;

import java.io.IOException;

import org.apache.jute.Record;
import org.apache.zookeeper.txn.TxnHeader;

/**
 * Interface for reading transaction logs.
 *
 */
public interface TxnLog {

	/**
	 * an iterating interface for reading transaction logs.
	 */
	public interface TxnIterator {
		/**
		 * close files and release the resources
		 * 
		 * @throws IOException
		 */
		void close() throws IOException;

		/**
		 * return the transaction header.
		 * 
		 * @return return the transaction header.
		 */
		TxnHeader getHeader();

		/**
		 * return the transaction record.
		 * 
		 * @return return the transaction record.
		 */
		Record getTxn();

		/**
		 * go to the next transaction record.
		 * 
		 * @throws IOException
		 */
		boolean next() throws IOException;
	}

	/**
	 * Append a request to the transaction log
	 * 
	 * @param hdr the transaction header
	 * @param r   the transaction itself returns true iff something appended, otw
	 *            false
	 * @throws IOException
	 */
	boolean append(TxnHeader hdr, Record r) throws IOException;

	/**
	 * close the transactions logs
	 */
	void close() throws IOException;

	/**
	 * commmit the trasaction and make sure they are persisted
	 * 
	 * @throws IOException
	 */
	void commit() throws IOException;

	/**
	 * the dbid for this transaction log.
	 * 
	 * @return the dbid for this transaction log.
	 * @throws IOException
	 */
	long getDbId() throws IOException;

	/**
	 * the last zxid of the logged transactions.
	 * 
	 * @return the last zxid of the logged transactions.
	 * @throws IOException
	 */
	long getLastLoggedZxid() throws IOException;

	/**
	 * Start reading the transaction logs from a given zxid
	 * 
	 * @param zxid
	 * @return returns an iterator to read the next transaction in the logs.
	 * @throws IOException
	 */
	TxnIterator read(long zxid) throws IOException;

	/**
	 * roll the current log being appended to
	 * 
	 * @throws IOException
	 */
	void rollLog() throws IOException;

	/**
	 * truncate the log to get in sync with the leader.
	 * 
	 * @param zxid the zxid to truncate at.
	 * @throws IOException
	 */
	boolean truncate(long zxid) throws IOException;
}
